Spatial light modulators are devices that may be used in a variety of optical communication and/or video display systems. These device generate an image by controlling a plurality of individual elements that deflect light to form the various pixels of the image. One example of a spatial light modulator is a digital micro-mirror device (“DMD”).
Typically, spatial light modulators, such as DMDs, operate by pulse width modulation (“PWM”). Generally, the incoming data signal or image is digitized into samples using a predetermined number of bits for each element. This predetermined number of bits is often referred to as the “bit-depth” of the modulator, particularly in systems employing binary bit weights. Generally, the greater the bit-depth, the greater the number of colors (or shades of gray) the modulator can display. For spatial light modulators, the number of bits assigned to a pixel typically depends on the perceived brightness for the pixel for a particular frame. Thus, the greater the value of the pixel code associated with the pixel, the greater the amount of time the pixel is illuminated during the frame. The most significant bit (“MSB”) is displayed the longest amount of time during the frame, while the least significant bit (“LSB”) is displayed the shortest amount of time during the frame. The size (or duration) of shortest LSB sets the brightness resolution (or bit-depth) that can be achieved for the pixel.
Since greater bit-depth can be used to produce greater detail in images, it is often desirable to increase the bit-depth of a video display system. Furthermore, increasing the bit-depth of the display system may reduce spatial contouring artifacts and/or temporal artifacts due to quantization noise. Unfortunately, the bit-depth of spatial light modulator-based display systems is limited by on the minimum size of the LSB, which is in turn limited by the minimum transition time of the individual elements of modulator. Some attempts at increasing the effective bit-depth of video display system have used dithering techniques, such as Blue-Noise STM, to overcome this limitation. However, these techniques, while increasing the effective number of bits (and thus end-user perceivable bit-depth) available via spatial and temporal dithering, may cause temporal dither noise that is noticeable in the images produced by the display systems.